GRO J1655-40
Michelle Buxton , Stephane Vennes, PASA, 18 (1), in press.
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Results
We found during initial tests that gravity was not well constrained as it is primarily determined by H. Our spectra do not cover any other Balmer lines which could be used to determine more accurately. Therefore, was fixed at 3.7 (Israelian et al. 1999). We also found that the fits were better for the F-star spectra with = 1 kms-1 and for GRO J1655-40 = 2 kms-1. Limb darkening for GRO J1655-40 was set at 0.5 (Allen 1963, Andersen, Clausen & Nördstrom 1984).
We tested our program on the solar spectrum convolved to our instrument resolution. The result is shown in Figure 3(a). The fit is good and our best-fit parameters are given in Table 4 with a comparison to published values. Another test was made on our F-star template spectra. We show a typical fit to one F-star (HR 5455) in Figure 3(b) and note that this also is a good fit, consistent with the literature (Table 5). Therefore, we are confident that our program is working satisfactorily.
Figure 4 and Table 6 give the fit result for GRO J1655-40. Our fitting code gives = 80 10 kms-1 (1).
Taking our value for and K2 = 215 kms-1 (Shahbaz et al. 1999), we find using equations (1) and (2) that q = 0.31 0.08. Therefore, from equation (3) and taking i = 67.20 3.50o (van der Hooft et al. 1998), M1 = 7.91 3.79 M (1). From q, we infer M2 = 2.76 1.79 M (1). These results agree well with Orosz & Bailyn (1997) and Shahbaz et al. (1999) as well as other published results (Table 1).
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Next Section: Discussion
Title/Abstract Page: Atmospheric Modelling of the
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© Copyright Astronomical Society of Australia 1997